It is perhaps not the best omen for US foreign affairs. Local historians in Wexford have discovered that George Bush is a descendant of Strongbow, the power-hungry warlord who led the Norman invasion of Ireland thus heralding 800 years of mutual misery. With a long line of Scots Irish presidents including Woodrow Wilson, the Irish are normally quick to claim US leaders as their own. But, despite President Bush's large Ulster Scots vote in the American Bible belt, Ireland had let his family escape the genealogical microscope.

But now Ann Griffin Bernstorff, an artist working on a tapestry to commemorate Ireland's Norman heritage, has discovered what she claims is the Bushs' missing Irish link.

Ms Griffin Bernstorff was researching Strongbow's son-in-law, William Marshal, when she discovered the connection. A descendant of Marshal married Anne Marbury Hutchinson, a famous 16th century religious dissenter who had already been linked to Mr Bush.

"It is one of those bizarre developments," she said. "We traced the Bush genealogy through a Republican source in Chicago and found it was correct. People here are absolutely shocked. I'm not sure what the wider reaction will be, Bush has not been seen as a great friend of the Irish."

Indeed, when Mr Bush visited a County Clare castle last year, radio talk-show hosts asked: "Is this the most hated American ever to set foot on Irish soil?"

The US president's now apparent ancestor, Richard de Clare, Earl of Pembroke - known as Strongbow for his arrow skills - is remembered as a desperate, land-grabbing warlord whose calamitous foreign adventure led to the suffering of generations. Shunned by Henry II, he offered his services as a mercenary in the 12th-century invasion of Wexford in exchange for power and land. When he eventually died of a festering ulcer in his foot, his enemies said it was the revenge of Irish saints whose shrines he had violated.

The Bush clan - who pride themselves on a distinguished New England family history that can be traced back to the first English in America - may well be looking for a healthy spin on the news. But it seems that Strongbow is not the worst of Bush's newfound ancestors.

The genetic line can also be traced to Dermot MacMurrough, the Gaelic king of Leinster reviled in history books as the man who sold Ireland for personal gain.

Even before MacMurrough earned the title of Ireland's worst traitor by inviting Strongbow's invasion to save himself from a local feud, the Irish chieftain had a reputation for gore. One English chronicler told how MacMurrough, recognising the features of a personal enemy poking from a pile of severed heads after a battle, snatched up the rotting flesh and tore it with his teeth in a "hideous frenzy".

As if it were not enough to be related to two of the most notorious figures in Irish history, Mr Bush's ancestors are also thought to have founded the settlement of New Ross, in County Wexford. A quiet place, New Ross has a stunning Norman church and another claim to fame: it is the ancestral home of John F Kennedy.

During his first election campaign in 2000, English genealogists found that Mr Bush was descended from Essex yeomanry. But unlike many US presidents keen to impress the Irish-American voters, he never before claimed an Irish link.

In the recent election campaign, the Democrat John Kerry had to deny rumours he was Irish. But Ronald Reagan and John F Kennedy played the Irish card. And Bill Clinton, perhaps aware that portraits of JFK hung beside the Pope above rural Irish fireplaces, once punched the air at a St Patrick's Day parade, declaring: "I feel more Irish each day."

The jury is out on whether Strongbow had a "conquering" gene that drove him to invade. Michael Staunton, a lecturer in history at University College Dublin, felt Strongbow was simply desperate. "It was a typical colonial situation, the people who don't have much going for them decided to hop off to another country."

Perhaps the most worrying question in New Ross is whether Mr Bush now has a claim on Leinster. "Yes of course, he probably does," Ms Griffin Bernstorff said. "But there are other families in the area who have a claim and neighbours and friends here would put up a pretty stiff fight."